How can I monitor air flow volume CFM along with boost?

[CRiggan]

Does anyone know of a guage or method to monitor the amount of air flowing into the engine. I know that boost can be monitored but how can you monitor the actual air flow volume? Is there some kind of mass air flow sensor that you could place before the air intake horn to do this that would not restrict the flow? Or could you take away the intake heater, cut out the grids and install a meter here?



Not sure and have no idea how to do this. It is probably not a good idea to take out the intake heater. Maybe install the meter right before the intake air horn.





2005 CTD,



Thanks

 

[JayWm]

Several have discussed monitoring drive pressure, not sure if that's what you're talking about. What are you hoping to watch for or accomplish or what is your concern? If we know what you want to accomplish or are concerned about others may be able to give you an idea.



Jay

 

[Diesel Power]

BOOST IS A MEASURE OF AIR FLOW, RIGHT NOW BOOST PRESSURE IS ALL WE HAVE! :-laf

 

[betterthanstock]

Does anyone know of a guage or method to monitor the amount of air flowing into the engine.

A 360 cubic inch 4 stroke engine lets in half its capacity (or 180 ci) every revolution. One atmosphere is 15 psi, so at 15 psi boost that's twice the volume squeezed in, and at 30 psi that's three times the volume of normal atmosperic air.

So at 3000 rpm at 30 psi boost you have 3000 x 3 x 180 / 1728 = 937 cfm.



That's about what you want your air filter rated for.



At 2000 rpm 15 psi you have 2000x2x180/1728=417 cfm



If you measure at the inlet to engine, it will be a little more (because it heats up in the turbo) than just rpm x 180/1728 of compressed air at whatever the boost guage shows.



All of the above assume 100% ingestion of all the air, which is not true since the valves/ports have restriction, as does the exhaust, so the actual volume will be 60-80% of the above. So an air filter rated for 0. 8 x 937 = 750 cfm will be acceptable.



There are laboratory flowmeters available, some measure volume, others measure mass. There are some parameters inside our ECM that could tell you the cfm based on calculations of intake temperature, boost and rpm, and assumptions about the exhaust restriction.



Since this is not a fixed-ratio mixture like gas engines, we don't care about the exact amount of air going in. Use an exhaust pyrometer to see if you have too much air (cold) or too much fuel (hot).

 

[JThiessen]

THere was a huge discussion about a year or so ago over on the DieselTruckResource site by DLeno and a memeber from Alsaka. SOme very informative and well thought out testing was done. Boost is a measure of pressure, not air flow. Just like on an air compressor, you can vary your pressure (PSI) independantly of air flow (CFM). You could therotically measure your flow where the current sensor is, utilize the map sensor reading to determine ambient air pressure/temperature, and have a reading of mass air flow.